Configuration Details:

Squid defaults to deny GET and HEAD requests with request entities,
as the meaning of such requests are undefined in the HTTP standard
even if not explicitly forbidden.
Set this directive to on if you have clients which insists
on sending request entities in GET or HEAD requests. But be warned
that there is server software (both proxies and web servers) which
can fail to properly process this kind of request which may make you
vulnerable to cache pollution attacks if enabled.